Compressive Behavior of FRP–UHPC/ECC–Steel Double-Skin Tubular Columns under Eccentric Loading

Hybrid double-skin tubular columns (DSTCs), which consist of an outer fiber-reinforced polymer (FRP) tube, an inner steel tube, and a concrete annular layer between the two tubes, possess many advantages, such as high load resistance and large deformation capacity and excellent durability. The use of ultrahigh-performance concrete (UHPC) or engineered cementitious composites (ECCs) instead of normal strength concrete (NSC) in the annular layer, given the advantages such as the ultrahigh strength of UHPC and strain hardening and high toughness feature of ECC, endows the DSTCs with additional high performance, such as an enhanced load-carrying capacity (with UHPC) and an improved cracking resistance (with ECC). The behavior of such DSTC specimens with UHPC or ECC that are subjected to eccentric loading was investigated for the first time, to the best of the authors' knowledge, and the results are reported in this paper. The DSTC specimens with NSC and ECC under eccentric compression exhibited similar great ductility with a bilinear shape for the axial load–deformation curves. In addition, the initial cracking of the FRP tube at the tension side of DSTC specimens with ECC or NSC occurred later than that of DSTC specimens with UHPC, which might imply the better durability performance of DSTC specimens with ECC or NSC during the serviceability state.